There is required a heat insulating film which is formed on a surface to improve a heat insulating efficiency and flame retardance. In Patent Document 1, a coating film is disclosed which has a high surface hardness and can prevent the surface from being damaged. The coating film is formed by dispersing hollow particles made of silica shells in a binder. By a wear resistance and high hardness of the hollow particles made of silica shells, the wear resistance of a substrate on which the coating film is formed can be improved. Additionally, the flame retardance can be improved by heat insulating properties of the hollow particles made of the silica shells.
In Patent Document 2, there is disclosed an internal combustion engine including a structural member having an improved heat insulating performance. In the internal combustion engine of Patent Document 2, a heat insulating material is disposed adjacent to an inner wall of an exhaust passage, and a high-temperature operative gas (an exhaust gas) flows along through channels made of the heat insulating material. In the heat insulating material, mesoporous silica sphere (MSS) particles having an average particle diameter of 0.1 to 3 μm are laminated in a state where the respective particles are densely bonded to one another via a bonding material. In the MSS particles, an infinite number of mesopores having an average pore diameter of 1 to 10 nm are formed.